Add counting-bits solution

Author: Jeehay28

counting-bits/Jeehay28.js

@@ -0,0 +1,51 @@
+// ✅ Time Complexity: O(n)
+// ✅ Space Complexity: O(n)
+
+/**
+ * @param {number} n
+ * @return {number[]}
+ */
+var countBits = function (n) {
+  // dp[i] = 1 + dp[i - MSB]
+  // MSB(Most Significant Bit)
+
+  let dp = new Array(n + 1).fill(0);
+  let msb = 1;
+
+  for (let i = 1; i <= n; i++) {
+    if (msb * 2 === i) {
+      msb = i;
+    }
+
+    dp[i] = 1 + dp[i - msb];
+  }
+
+  return dp;
+};
+
+// ✅ Time Complexity: O(n * logn)
+// ✅ Space Complexity: O(n)
+
+/**
+ * @param {number} n
+ * @return {number[]}
+ */
+// var countBits = function (n) {
+//   let result = [0];
+//   const count = (num) => {
+//     let cnt = 0;
+//     while (num !== 0) {
+//       cnt += num % 2;
+//       num = Math.floor(num / 2);
+//     }
+//     return cnt;
+//   };
+
+//   for (let i = 1; i <= n; i++) {
+//     const temp = count(i);
+//     result.push(temp);
+//   }
+
+//   return result;
+// };
+